This may be unusual, but this thing just clicked in my mind. What should someone write in an email to inform their (would-be) new employer that they have posted their resignation from the current(soon would-be past) company. Also, a follow up could be a request to extend extend the joining date(or start date, as it may be called) for some reasons? The email should be polite and is more of a request to delay the joining date. Nobody would like to be rude in the email, when a new partnership is about to begin.